Japanese Patent Laid-Open Publication No. 54-114878 discloses a coolant supply device in which a coolant and air is supplied through a through-hole provided in a drawing bolt.
A coolant is supplied to a tool and a work during working to provide a cooling action, an abrasion preventive action and the like. On the other hand, air is supplied when the tool is unclamped to prevent chips or the like from adhering to a shank portion of a tool holder and a tool holder support portion of a spindle, thus enhancing the mounting accuracy of the tool.
In the aforementioned coolant supply device, the through-hole through which a coolant and air are supplied is used in common over the whole channel. An outlet is also used in common, and both the coolant and air are discharged out of the common outlet on the diametrically central part.
A hole for allowing a coolant to flow is provided on the diametrically central part of the tool holder, and the coolant moved out of the outlet is supplied to the tool and the work through the hole of the tool holder. The air as well as the coolant are discharged along the diametrically central part from the common outlet.
The shank portion of the tool holder and the tool holder support portion of the spindle to be cleaned are not present on the diametrically central part but are spread on the circumference encircling the diametrically central part. Because of this, it sometimes occurred that the cleaning operation by way of air discharged is not sufficient so that a improper setting of the tool is brought forth.